linux-kernel - Re: [RFC][PATCH] procfs: Add /proc/<pid>/mapped

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Message-ID: <CAAHN_R0AhAc7zt3sfbKdXJEj3Ncd4Hao-1qr=X3mkSjB7F_fYg@mail.gmail.com>
Date:	Wed, 14 Jan 2015 20:07:06 +0530
From:	Siddhesh Poyarekar <siddhesh.poyarekar@...il.com>
To:	Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:	Calvin Owens <calvinowens@...com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Oleg Nesterov <oleg@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Peter Feiner <pfeiner@...gle.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	linux-kernel <linux-kernel@...r.kernel.org>, kernel-team@...com
Subject: Re: [RFC][PATCH] procfs: Add /proc/<pid>/mapped_files

On 14 January 2015 at 19:43, Rasmus Villemoes <linux@...musvillemoes.dk> wrote:
> Just thinking out loud: Could one simply mark a VMA as being used for
> stack during the clone call (is there room in vm_flags, or does
> VM_GROWSDOWN already tell the whole story?), and then write the TID into
> a new field in the VMA - I think one could make a union with vm_pgoff so
> as not to enlarge the structure.

vm_flags does not have space IIRC (that was my first approach at
implementing this) and VM_GROWSDOWN is not sufficient.  If we can make
a union with vm_pgoff like you say, we probably don't need a flag
value; a non-zero value could indicate that it is a thread stack.

One problem with caching the value on clone like this though is that
the stack could change due to a setcontext, but AFAICT we don't care
about that for the process stack either.

Siddhesh
-- 
http://siddhesh.in
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